Laundry machine, control and method

ABSTRACT

The present invention relates to a method for determining load size in a washing machine. A sensor detects the water level, step 51, in the machine before a recirculation pump is activated, step 50, and after it is de-activated, steps 52-54. The load size can be calculated from the difference in water level, steps 55, 56.

FIELD OF THE INVENTION

The present invention relates to laundry machines and in particular to laundry washing machines having a laundry basket for holding a laundry load and a pump for recirculating wash liquid into the basket.

SUMMARY OF THE PRIOR ART

In 1991 Fisher & Paykel Limited released the first model of their SMARTDRIVE washing machines. This machine included a cabinet, a tub suspended within the cabinet by a plurality of suspension rods extending between the top edge of the cabinet and a lower portion on the tub. A single shaft extended through the base of the tub. The stator of a salient pole electronically commutated brushless DC motor was fixed to the lower side of the tub base. An external permanent magnetic rotor was fitted to the lower end of the shaft to substantially surround the stator. Within the tub a spin basket was supported for rotation on the shaft. Within the spin basket an agitator was fixed to the upper end of the shaft. The agitator was of a central post type with three lateral vanes and a generally conical base portion. The spin basket was supported by the shaft at a lower position, was free to rise on the shaft to an upper position. The spin basket included downwardly facing hollow chambers. Vertical support of the spin basket on the shaft in the lower position included inter-engagement of a downwardly facing castellated clutch on the spin basket and an upwardly facing castellated clutch fixed to the shaft. Accordingly without sufficient wash liquid in the tub for the spin basket and any associated load to float the spin basket remained rotationally fixed to the shaft. With sufficient wash liquid in the tub the float chambers of the spin basket would provide for the basket and load to float and disengage from the shaft such that the spin basket and shaft would rotate. This arrangement is described in U.S. Pat. No. 5,353,613. This direct drive electronically controlled laundry machine has been very successful.

U.S. Pat. No. 6,212,722 proposes an improved laundry washing machine for domestic use. This machine is of the top loading type having an outer bowl, a wash basket within the outer bowl and access to the wash basket through a top opening. A motor is provided to drive rotation of the wash basket within the outer bowl. A wash plate is provided in the lower portion of the wash basket to be rotated by the motor with the wash basket or independently of the wash basket. The patent proposes a combination of water level control, wash plate design, wash basket design and movement pattern for the wash plate which leads to an inverse toroidal movement of the laundry load during a wash phase. The sodden wash load is dragged radially inward on the upper surface of the wash plate and progresses upward in the region of the centre. The sodden wash load then progresses radially outward to the wall of the wash basket and downward to the base of the wash basket. This has been found to provide an effective wash action with low water consumption.

When a wash system of the type disclosed in U.S. Pat. No. 6,212,722 is applied to a machine of the type described in U.S. Pat. No. 5,353,613, the water volume required to operate the floating clutch can be a significant factor in overall water consumption.

The floating clutch has also provided a method of determining the size of the wash load. Disconnection of the spin basket from the agitator shaft can be detected by feedback from the drive motor. The water level in the tub at the time of disconnection indicates the mass of the laundry load.

However for very low water consumption wash modes water levels may be desirable that are insufficient to float the spin basket.

Alternative clutch arrangements are known involving twin drive shafts passing through the tub, with an external active clutch, or an external lost motion clutch. Alternatively we have proposed in an earlier patent application a lost motion clutch located within the tub acting between the agitator shaft and the spin basket.

These arrangements fail to provide a solution to detecting the wash load in a very low water level wash mode.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a laundry machine, a control for a laundry machine, or a method which goes some way toward overcoming the above disadvantages or which will at least provide the public with a useful choice.

In one aspect the present invention may be said to consist in a laundry machine comprising: a spin basket, a sump below said spin basket, a drive assembly for rotating said spin basket, a pump for recirculating wash liquid from said sump into said spin basket, a water level sensor for measuring the water level in said sump and providing an output, a controller connected to receive said output from said water level sensor and control activation of said pump, said controller programmed to determine a size of a laundry load held in said spin basket based on analysis of changing water level in the sump.

Preferably, said analysis relating to the rate at which free wash liquid drains from a saturated laundry load and collects in said sump and/or the volume of free wash liquid held by the saturated clothes load during recirculation.

Preferably, said analysis uses water level output from said sensor under two operating conditions: with the pump recirculating wash liquid into the spin basket, and with the pump not recirculating wash liquid into the spin basket.

Preferably, said analysis uses water level output from said sensor read on at least two occasions, at least one said occasion being after ceasing to recirculate wash liquid in the spin basket.

Preferably, said controller is programmed to determine a size of a laundry load held in said spin basket by comparing a first water level output taken while recirculating water through said wash basket with a second water level output taken after ceasing to recirculate water through said wash basket.

Preferably, said second water level output is taken a predetermined time after ceasing to recirculate wash liquid through said basket.

Preferably, said second water level output is taken at a time when free liquid in the laundry load would not be expected to be completely drained to the sump for any of the normal washload sizes.

Preferably, said laundry machine comprises a tub (or enclosure), said drive assembly includes a shaft extending through a wall of said tub (or enclosure) and said spin basket is supported within said tub (or enclosure) for rotation about the same rotation axis as said shaft, said sump being, or being located at, the lower portion of said tub (or enclosure) such that liquid in said tub (or enclosure) collects at said sump.

Preferably, said spin basket is supported by said shaft.

Preferably, said shaft rotates around a vertical axis, and said tub and said spin basket are accessible through a top opening.

Preferably, said laundry machine comprises an agitator in said spin basket, driven by said drive assembly, and a clutch for selectively connecting said spin basket to said drive assembly.

Preferably, said shaft of said drive assembly protrudes from below a base portion of said tub, a stator of an electric motor is fixed to said tub, and a rotor of said electric motor is fixed to said shaft.

Preferably, said laundry machine comprises a cabinet, and a plurality of suspension members extending between an upper portion of said cabinet and a lower portion of said tub, said suspension members supporting said tub, spin basket, drive assembly and motor within said cabinet.

Preferably, said motor is of the external rotor type.

Preferably, said laundry machine includes a power supply circuit connected with windings of said motor, and said controller has outputs connected to said power supply circuit for controlling the application of power to said windings of said motor, said controller being programmed to drive said drive assembly in at least a first mode involving s slow rotation of said spin basket while said pump recirculates wash liquid into said spin basket.

Preferably, said basket is supported to rotate about a horizontal or inclined axis.

Preferably, a nozzle adjacent an open end of said basket directs recirculating water onto the laundry load.

Preferably, said basket is supported by a shaft at both ends to rotate around a horizontal or inclined axis, and wherein an access hatch or door is provided in the side surface of said wash basket.

Preferably, recirculating wash liquid is provided to said basket along one or both supporting shafts.

In another aspect the present invention may be said to consist in a control for execution in a laundry machine having: a spin basket, a sump below said spin basket, a drive assembly for rotating said spin basket, a pump for recirculating wash liquid from said sump into said spin basket, and a water level sensor for measuring the water level in said sump and providing an output; said control determining a size of a laundry load held in said spin basket based on analysis of changing water level in the sump.

Preferably, said analysis relating to the rate at which free wash liquid drains from a saturated laundry load and collects in said sump and/or the volume of free wash liquid held by the saturated clothes load during recirculation.

Preferably, said analysis uses water level output from said sensor under two operating conditions: with the pump recirculating wash liquid into the spin basket, and with the pump not recirculating wash liquid into the spin basket.

Preferably, said analysis uses water level output from said sensor read on at least two occasions, at least one said occasion being after ceasing to recirculate wash liquid in the spin basket.

Preferably, said controller is programmed to determine a size of a laundry load held in said spin basket by comparing a first water level output taken while recirculating water through said wash basket with a second water level output taken after ceasing to recirculate water through said wash basket.

Preferably, said second water level output is taken a predetermined time after ceasing to recirculate wash liquid through said basket.

Preferably, said second water level output is taken at a time when free liquid in the laundry load would not be expected to be completely drained to the sump for any of the normal washload sizes.

In another aspect the present invention may be said to consist in a method of determining the size (weight) of a laundry load in a laundry machine, the machine having a spin basket, a sump below said spin basket, a drive assembly for rotating said spin basket, a pump for recirculating wash liquid from said sump into said spin basket, and a water level sensor for measuring the water level in said sump and providing an output, said method comprising: determining a size of a laundry load held in said spin basket based on analysis of changing water level in the sump.

Preferably, said analysis relating to the rate at which free wash liquid drains from a saturated laundry load and collects in said sump and/or the volume of free wash liquid held by the saturated clothes load during recirculation.

Preferably, said analysis uses water level output from said sensor under two operating conditions: with the pump recirculating wash liquid into the spin basket, and with the pump not recirculating wash liquid into the spin basket.

Preferably, said analysis uses water level output from said sensor read on at least two occasions, at least one said occasion being after ceasing to recirculate wash liquid in the spin basket.

Preferably, said controller is programmed to determine a size of a laundry load held in said spin basket by comparing a first water level output taken while recirculating water through said wash basket with a second water level output taken after ceasing to recirculate water through said wash basket.

Preferably, said second water level output is taken a predetermined time after ceasing to recirculate wash liquid through said basket.

Preferably, said second water level output is taken at a time when free liquid in the laundry load would not be expected to be completely drained to the sump for any of the normal washload sizes.

In this specification where reference has been made to patent specifications, other external documents, or other sources of information, this is generally for the purpose of providing a context for discussing the features of the invention. Unless specifically stated otherwise, reference to such external documents is not to be construed as an admission that such documents, or such sources of information, in any jurisdiction, are prior art, or form part of the common general knowledge in the art

The term “comprising” as used in this specification means “consisting at least in part of”. Related terms such as “comprise” and “comprised” are to be interpreted in the same manner.

To those skilled in the art to which the invention relates, many changes in construction and widely differing embodiments and applications of the invention will suggest themselves without departing from the scope of the invention as defined in the appended claims. The disclosures and the descriptions herein are purely illustrative and are not intended to be in any sense limiting

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cutaway perspective view of a laundry machine according to one embodiment of the present invention.

FIG. 2 is a block diagram of a control system for a laundry washing machine.

FIG. 3 is a cross-sectional side elevation of a lower part of the tub and spin basket, the agitator and an upper part of the drive shaft according to a preferred embodiment of the present invention.

FIG. 4 is a plot of test data illustrating the relationship between the water level difference (when recirculating and not-recirculating) and wash load size.

FIG. 5 is a flow diagram of a method for determining load size.

DETAILED DESCRIPTION

A laundry machine that may incorporate a control according to the present invention is illustrated in FIG. 1.

The example laundry machine includes a cabinet 100 with a lid 102 and a user console 104. A controller 106 is located within the body of the user console. The controller 106 includes a power supply and a programmed microcontroller. The power supply receives power from the mains supply and supplies power to the microcontroller, to a power supply bridge for the electric motor and to ancillary devices within the machine such as a pump and valves. Delivery of power to the motor 114 and the ancillary devices is at the control of the microcontroller. The microcontroller receives inputs from a user interface on console 104.

A tub 120 is supported within the cabinet. The tub is preferably suspended from the upper edge of the cabinet, for example by suspension rods 121. The tub may alternatively be supported from below or from the sides of the cabinet. A wash or drain pump is fitted to the lower portion of the tub. The pump is preferably located at a sump portion of the tub.

A wash basket 122 is supported for rotation within the tub. Opening the lid 102 provides user access to an upper open end of the wash basket.

An agitator 124 is mounted in the lower portion of the wash basket. The agitator may be of a central post type, with or without additional moving parts, such as augers, or of a wash plate type, such as illustrated in U.S. Pat. No. 6,212,722, or of a pulsator type, or of any other type having independent movement from wash basket 122. The illustrated agitator is of wash plate type, intended for facilitating low water level wash exhibiting inverse toroidal rollover patterns.

The improvements and adaptations of the present invention are preferably implemented in a laundry machine of a direct drive type with motor fixed directly to the external end of a single drive shaft. However other drive systems involving for example gearbox or belts driving a single or multiple drive shafts may alternatively be used.

A motor 114 below the tub directly drives single shaft 128. The single shaft 128 extends through the lower face of the tub, where it is supported in a pair of bearings 130. A seal 360 prevents water escaping the tub at the interface between the tub and shaft.

The wash basket 122 is mounted on the shaft within the tub. The wash basket may typically comprise a base 132 and a perforated cylindrical skin 134. The perforated cylindrical skin extends up from the base to define an open ended drum. The wash basket may include a balance ring at the upper edge of the cylindrical skin.

The wash plate 124 is also fitted to the shaft, within the wash basket 122.

A clutch arrangement 142 is provided to enable the motor 114 to selectively drive either the wash plate 124 independently of the wash basket 122, or drive the wash basket 122. In driving the wash basket the motor may also drive the wash plate. Various mechanisms have been proposed to accomplish this selective drive. One example mechanism is described here which promotes low water consumption while retaining a drive assembly where a single shaft penetrates the tub 120. This mechanism, which is not yet published in the prior art but is not itself the subject of the present invention, is described in detail below.

The controller is part of a control system for coordinating the operations of the laundry machine. The control system is illustrated in the block diagram of FIG. 2. The controller includes a microcontroller 800. The microcontroller may include a microcomputer and ancillary logic circuits and interfaces. The microcontroller receives user input commands on user interface 802. The user interface may include, for example, a plurality of touch controls such as switches or buttons, or may include a touch screen, or may include rotary or linear selection devices. The microcontroller may include a display device 804 to provide feedback to a user. The display device may comprise a plurality of indicators, such as lights or LEDs, or may include a screen display. The display device 804 and the user interface 802 may be mounted to a single module incorporating the nicrocontroller.

The microcontroller may be a microcomputer including processor, memory and input and output registers. Alternatively the microcontroller may be based on a programmable logic device, or permanently configured logic circuit.

The microcontroller receives power from a power supply 806. The microcontroller also controls power switches 808 applying power from supply 806 to drive motor 810. The microcontroller controls further power switches 812 applying power from supply 806 to a pump 814. The 20 microcontroller also controls a power switch 830 applying power to a cold water inlet valve 832 and a power switch 834 applying power to hot water inlet valve 836.

The microcontroller preferably receives feedback from position sensors 816 associated with the motor. These sensors may for example be a set of digital Hall sensors, sensing changes in rotor position, or may be any suitable encoder. Alternatively rotor position and movement may be sensed from motor drive current or EMF induced in unenergised motor windings.

The microcontroller also preferably receives input from a water level sensor 818, which detects the level of water in the tub of the machine, and from a temperature sensor 820 which detects the temperature of water being supplied to the wash tub.

In an agitation phase of a wash cycle the preferred controller applies an initial wash plate drive profile to initiate the inverse toroidal motion. Other low water consumption wash cycles utilising wash liquid recirculation have also been proposed in the prior art, and the present invention relates to these other low water consumption wash cycles as well. For the toroidal wash motion the initial drive profile in the agitation phase is characterised by higher angular velocity and longer stroke length to start the clothes movement. This movement is subsequently maintained by a maintenance drive profile with lower angular velocity and stroke length. Many drive systems are possible for controlling wash plate drive profiles. One example is described in U.S. Pat. No. 5,398,298.

The initial drive profile is varied according to load size. The profile is more vigorous for larger load sizes. The maintenance drive profile may also be varied according to load size. Again the profile is more vigorous for larger load sizes.

Load size may be determined from a user entry or selection, but preferably the load size is automatically determined in accordance with the control and method of the present invention.

Load size may also be used to determine fill volumes for deeper wash or rinse phases of the wash cycle. Load type may also be determined partly based on the load size measurements. Load type determination may influence the type or agitator stroke selected by the controller. The output of the preferred control may be used in all of these control decisions.

The control of the present invention automatically determines load size by a combination of monitoring the water level and selectively activating the recirculation pump. The water level may be monitored continuously or may be checked at selected intervals or selected times. The method is capable of wide variation without departing from the general scope of the invention. Some potential implementations will be more advantageous than others, and the particular method presented appears simple and reliable.

The method utilises the discovery that during recirculation the saturated wash load holds a volume of free water that is closely related to the load size. This relationship seems to be largely independent of the composition (fabric type) of the laundry load. By load size we mean weight. By free water we mean water that will drain quickly from the wash load after recirculation ends. During recirculation this free water is draining through the laundry load and through the various openings in the wash basket to return to the sump. Some free water will also be airborne. Some water may also return to the sump from the recirculation conduits.

Furthermore the inventor has discovered that the rate of flow of this free water back to the sump after the recirculation ends is closely related to the load size. Again this relationship seems to be largely independent of the composition of the laundry load.

Accordingly the preferred control of the present invention measures the water level at the sump during steady state recirculation where there has been sufficient water to fully saturate the load. The control also measures the water level in the sump with the same total volume of water in the machine and with the load fully saturated, but where the recirculation is inactive. The difference in water levels is related to the load size.

In the most preferred control the water level is measured first during recirculation, then recirculation is halted and after a predetermined time the water level is measured again. The predetermined time is sufficiently short that the free water has not substantially completely drained from laundry load for any of the load sizes. The inventor believes that this provides more accurate results than allowing the free water to nearly completely drain from the load. This also provides faster results, and load size can be tested in time periods as short as 20 seconds.

EXAMPLE

The inventor conducted tests using a machine substantially as described with reference to FIGS. 1 and 3. The test involved loading the machine with laundry loads of different size and composition. The particular machine retained a spin basket with certain formations to assist flotation, although the spin basket was constrained to not float. This influences the method to use a slightly deeper water level during the test phase to avoid some non-linearity in the relationship between water volume and water level. In practise the increased water level doesn't harm overall consumption as this test is conducted while entering a wash phase that uses a still greater volume of water. Alternatively the control could compensate for a non-linear relationship between volume and water level by applying a compensation function to the water level readings.

Test Method:

-   (1) Recirculation was conducted at a 50 mm water level (pump     speed=2000 rpm) with inlet water provided to maintain this level     while the load became fully saturated. -   (2) While continuing to recirculate, additional cold water was added     until the water level reached 100 mm. This placed the subsequent     observations in a water level range that had a linear relationship     between water level and water volume. -   (3) Waited for the water level to stabilise (5 seconds). This     allowed the water level to reach a steady state after the inlet     valve was turned off. -   (4) Recorded a first water level. -   (5) Turned off recirculation pump -   (6) Waited 15 secs. This delay was selected as being sufficient for     s substantial part of the free water to drain to the sump but not     substantially completely drain for any of the test wash loads. -   (7) Recorded a second water level, and calculated the increase in     water level (delta WL)

Results for 13 different loads (size and composition) are provided in Table 1 below. These results are plotted in the graph of FIG. 4.

TABLE 1 Load Size Delta WL (mm) (kg) Cotton Synthetic Towels 1 15 13 2 20 33 32 4 40 48 53 5.4 58 6 64 68 7.6 82 8 88

The plot shows the close linear relationship between the load size and the recorded increase in water level. Averaged across the loads the increase (in mm) was approximatey 11 times the load size (in kg). There is some variation the results for different load compositions, however this does not seem sufficient to create significant overlap between the results for different load sizes. The inventor expects that a control based on this relationship would operate as effectively or nearly as effectively as other automatic load size sensing controls.

Accordingly, referring to FIG. 5, in the preferred control the controller is programmed to perform, at any appropriate time during a wash cycle the steps:

-   -   1. Activate the recirculation pump, step 50.     -   2. While the recirculation pump is active and the water level is         in a steady state, read and record the water level indicated by         the output of the water level sensor (First water level), step         51.     -   3. Deactivate the recirculation pump, step 52.     -   4. Wait a predetermined period (eg: 15 seconds), step 53.     -   5. Read the water level indicated by the output of the water         level sensor (Second water level), step 54.     -   6. Subtract the first water level from the second water level to         give a water level increase, step 55.     -   7. Calculate a load size value from the water level increase,         step 56.

Calculation can be done, for example using a look-up table or relationship described in relation to Table 1.

Additional steps could be included to compensate for non-linearities in the water level to water volume, or to compensate for a nonlinear relationship between the water level increase and the load size (which could vary for machines of different structure or type).

Alternative implementations could monitor the water level to assess the rate of increase after stopping the recirculation pump. Still further implementations could use a high water level reading taken after the recirculation pump is switched back on, rather than before the pump is switched off. Still further implementations could look at two or more water level values taken at intervals after the pump is turned off. The inventor expects that these variations may work, but has not tested them.

The exemplary clutch mechanism is disposed within the tub of the laundry machine. In the embodiment illustrated in the drawings the mechanism is provided in the space between the wash plate 124 and the upper side of the base 322 of the spin basket.

The spin basket is rotatably supported on the shaft 128, for example by a pair of bearings 318. The spin basket is vertically supported on the shaft 128, for example by a thrust bearing 310.

The bearings 318 are fitted within bearing tube 320 of the base portion 322. The bearings 318 are preferably of a sliding seal type. The bearings 318 provide radial support of the spin basket relative to the shaft. The bearings are vertically spaced on the shaft to provide torsional stability.

The thrust bearing 310 is fitted to the shaft 128 above the upper radial bearing 318. The thrust bearing 310 preferably engages over a spline 313. The thrust bearing 310 has an upwardly facing thrust surface which supports the weight of the spin basket. The lower edge of the thrust bearing 310 is supported on a shoulder 317 of the shaft 128. A support hub 308 rests on the thrusts surface of thrust bearing 310 and is secured to an upper face of the spin basket base 322. A lower surface 332 of the support hub 308 bears on thrust surface 334 of thrust bearing 310.

A drive ring 302 is mounted to rotate around the axis of shaft 128. The drive ring includes a drive lug 304 extending radially.

An end stop 306 extends, preferably upwardly, from the outer surface of base 322 of the spin basket. An end stop 300 extends, preferably downwardly, from the underside of wash plate 124. The end stop 306 and end stop 300 are positioned and configured such that they move past each other when the agitator rotates relative to the spin basket. In the illustrated arrangement the spin basket end stop 306 is radially inside the inner most extent of agitator end stop 300. The end stops could alternatively be vertically separated, or have other non-interfering complementary shape and location.

The drive lug 304 of drive ring 302 extends outwardly sufficient to interfere with both end stop 306 and end stop 300.

Either end stop may be in the form of a free standing lug. Alternatively the end stop may be an end portion of a ridge or other formation, so long as the end stops and the drive lug meet the interference requirements of the clutch.

The agitator 124 is fixed to the upper end of drive shaft 128. The agitator 124 rotates with drive shaft 128. Typically the drive will operate in a wash mode where the shaft is reciprocated in alternate directions, and a continuous rotation mode in which the shaft is rotated for longer periods in a single direction.

For the continuous rotation modes, the end stop 300 of the agitator drives around the drive lug 304 of drive ring 302 when it is rotating and in contact with the lug 304. Lug 300 continues to drive around the drive lug 304 until drive lug 304 contacts the end stop 306 of the spin basket. Drive lug 304 then in turn drives rotation of the spin basket by end stop 306. In this condition with rotation of the end stop 300 against lug 304 against end stop 306, rotation of the drive shaft drives rotation of the agitator and spin basket together.

From this drive position in a first direction the drive shaft may rotate relative to the spin basket through almost two full revolutions before meeting a second end condition where it drivingly engages the spin basket for rotation in the other direction. The agitator end stop 300 moves nearly one full revolution around the drive shaft 124 before engaging drive lug 304 on the same side as end stop 306. End stop 300 continues to drive drive lug 304 for almost one further complete revolution before the opposite side of drive lug 304 engages against end stop 306 of the spin basket. At this point rotation of the agitator would proceed to drive rotation of the spin basket via the first end stop, drive lug 304 and second end stop 306. However this point of rotation is nearly two full relative revolutions away from the other end condition, and so in a typical agitation stroke of up to 1.5 revolutions this condition is not reached.

In the illustrated embodiment end stop 306 is an upwardly extending lug at the perimeter of support hub 308. Support hub 308 includes a raised hub portion with an outwardly facing wall 338 and a perimeter flange 330. The lug 306 extends upward at the periphery of perimeter flange 330. The annular body 331 of drive ring 302 fits over the hub portion of the support hub 308, occupying the region inward of lug 306. Inner face 336 of ring 331 slides against outwardly facing surface 338 of support hub 308.

The support hub 308 is fixed to the upper face of the spin basket base 322, for example by fasteners 312. Practically, this allows assembly of the spin basket onto the drive shaft by first fitting the radial support bearings over the drive shaft, then fixing the thrust bearing 310 over the lower spline 313, then support hub 308 is fitted over the drive shaft and fastened to the spin basket base to support the spin basket on thrust bearing 310, then agitator 124 is fitted to the upper spline on the drive shaft and secured in place by fastener 350.

Typical agitator motion during the agitation mode is between 0.5 and 1.5 revolutions. So the almost two revolutions provided by the clutch of the present invention will generally be sufficient to absorb the agitation movement of the drive shaft without engaging to drive the wash basket at the end of each stroke.

The electronically commutated drive system may apply an upper limit to the agitator motion, for example an upper limit of 1.5 revolutions.

The clutch construction may be modified so that the impact at the end condition may be reduced. For example either end stop may be formed to be soft or springy. Alternatively the drive lug on the drive ring may be flexible, for example an outwardly extending leaf of spring steel, which may bend elastically with the impact between the end stops. Alternatively either end stop may have a friction clutch engagement to the respective support part (the spin tub or the drive assembly).

Other drive arrangements that allow selective driving of the agitator in alternate directions through a useful length of stroke without relying on high water levels are also suitable for use in low water consumption wash systems. These include arrangements with twin drive shafts and actively controlled clutches located outside the wash tub to connect between the twin shafts. The present control and method may also be used in machines that do not have a separately rotating agitator and spin basket. The control and method is more generally applicable, useful in all machines that have a recirculating wash system that can return water from a low water level sump to cover a laundry load held in the spin basket.

The control and method of the present invention can be applied to vertical axis washing machines or to horizontal axis washing machines or to washing machines having a spin basket rotating about an inclined axis. Recirculation systems can be implemented in each type of machine by spraying or discharging into the chamber of the spin basket from an outlet or nozzle. For example in a top loading vertical axis machine or a front loading horizontal axis or inclined axis machine the nozzle or outlet may be arranged to spray into the chamber from the periphery of the chamber opening. Alternatively, particularly in a horizontal axis machine, the wash liquid may be channeled through the shaft rotatably supporting the spin basket. This is particularly useful for a horizontal axis machine where the drum is supported at both ends and access is provided through a hatch or door in the circumference of the basket.

The basket may be supported in a wash tub that is independently supported from the housing or wrapper of the machine. Alternatively the wash tub may be an internal surface of the housing or may be rigidly supported in the housing. The lower portion of the tub may act as a general sump channeling water to the pump, or may include a specific sump depression to collect water more effectively.

Water level may be measured in many known ways. For example the water level sensor may use static water pressure or may use a conductivity sensor. The preferred water level sensor uses water pressure. The sensor may be located under or behind a cover or in a recess or channel to protect the sensor and reduce water flow effects. 

1. A laundry machine comprising: a spin basket, a sump below said spin basket, a drive assembly for rotating said spin basket, a pump for recirculating wash liquid from said sump into said spin basket, a water level sensor for measuring the water level in said sump and providing an output, a controller connected to receive said output from said water level sensor and control activation of said pump, said controller programmed to determine a size of a laundry load held in said spin basket based on analysis of changing water level in the sump.
 2. A laundry machine as claimed in claim 1 wherein said analysis relating to the rate at which free wash liquid drains from a saturated laundry load and collects in said sump and/or the volume of free wash liquid held by the saturated clothes load during recirculation.
 3. A laundry machine as claimed in either claim 1 or claim 2 wherein said analysis uses water level output from said sensor under two operating conditions: with the pump recirculating wash liquid into the spin basket, and with the pump not recirculating wash liquid into the spin basket.
 4. A laundry machine as claimed in either claim 1 or claim 2 wherein said analysis uses water level output from said sensor read on at least two occasions, at least one said occasion being after ceasing to recirculate wash liquid in the spin basket.
 5. A laundry machine as claimed in claim 4 wherein said controller is programmed to determine a size of a laundry load held in said spin basket by comparing a first water level output taken while recirculating water through said wash basket with a second water level output taken after ceasing to recirculate water through said wash basket.
 6. A laundry machine as claimed in claim 5 wherein said second water level output is taken a predetermined time after ceasing to recirculate wash liquid through said basket.
 7. A laundry machine as claimed in claim 5 wherein said second water level output is taken at a time when free liquid in the laundry load would not be expected to be completely drained to the sump for any of the normal washload sizes.
 8. A laundry machine as claimed in claim 1 including a tub (or enclosure), said drive assembly includes a shaft extending through a wall of said tub (or enclosure) and said spin basket is supported within said tub (or enclosure) for rotation about the same rotation axis as said shaft, said sump being, or being located at, the lower portion of said tub (or enclosure) such that liquid in said tub (or enclosure) collects at said sump.
 9. A laundry machine as claimed in claim 8 wherein said spin basket is supported by said shaft.
 10. A laundry machine as claimed in either claim 8 wherein said shaft rotates around a vertical axis, and said tub and said spin basket are accessible through a top opening.
 11. A laundry machine as claimed in claim 10 including an agitator in said spin basket, driven by said drive assembly, and a clutch for selectively connecting said spin basket to said drive assembly.
 12. A laundry machine as claimed in either claim 10 wherein said shaft of said drive assembly protrudes from below a base portion of said tub, a stator of an electric motor is fixed to said tub, and a rotor of said electric motor is fixed to said shaft.
 13. A laundry machine as claimed in claim 12 including a cabinet, and a plurality of suspension members extending between an upper portion of said cabinet and a lower portion of said tub, said suspension members supporting said tub, spin basket, drive assembly and motor within said cabinet.
 14. A laundry machine as claimed in claim 13 wherein said motor is of the external rotor type.
 15. A laundry machine as claimed in claim 14 wherein said laundry machine includes a power supply circuit connected with windings of said motor, and said controller has outputs connected to said power supply circuit for controlling the application of power to said windings of said motor, said controller being programmed to drive said drive assembly in at least a first mode involving s slow rotation of said spin basket while said pump recirculates wash liquid into said spin basket.
 16. A laundry machine as claimed in claim 8 wherein said basket is supported to rotate about a horizontal or inclined axis.
 17. A laundry machine as claimed in claim 9 wherein a nozzle adjacent an open end of said basket directs recirculating water onto the laundry load.
 18. A laundry machine as claimed in claim 8 wherein said basket is supported by a shaft at both ends to rotate around a horizontal or inclined axis, and wherein an access hatch or door is provided in the side surface of said wash basket.
 19. A laundry machine as claimed in claim 18 wherein recirculating wash liquid is provided to said basket along one or both supporting shafts.
 20. A control for execution in a laundry machine having: a spin basket, a sump below said spin basket, a drive assembly for rotating said spin basket, a pump for recirculating wash liquid from said sump into said spin basket, and a water level sensor for measuring the water level in said sump and providing an output; said control determining a size of a laundry load held in said spin basket based on analysis of changing water level in the sump.
 21. A control as claimed in claim 20 wherein said analysis relating to the rate at which free wash liquid drains from a saturated laundry load and collects in said sump and/or the volume of free wash liquid held by the saturated clothes load during recirculation,
 22. A control as claimed in either claim 20 or claim 21 wherein said analysis uses water level output from said sensor under two operating conditions: with the pump recirculating wash liquid into the spin basket, and with the pump not recirculating wash liquid into the spin basket.
 23. A control as claimed in either claim 20 or claim 21 wherein said analysis uses water level output from said sensor read on at least two occasions, at least one said occasion being after ceasing to recirculate wash liquid in the spin basket.
 24. A control as claimed in claim 23 wherein said controller is programmed to determine a size of a laundry load held in said spin basket by comparing a first water level output taken while recirculating water through said wash basket with a second water level output taken after ceasing to recirculate water through said wash basket.
 25. A control as claimed in claim 24 wherein said second water level output is taken a predetermined time after ceasing to recirculate wash liquid through said basket.
 26. A control as claimed in claim 24 wherein said second water level output is taken at a time when free liquid in the laundry load would not be expected to be completely drained to the sump for any of the normal washload sizes.
 27. A method of determining the size (weight) of a laundry load in a laundry machine, the machine having a spin basket, a sump below said spin basket, a drive assembly for rotating said spin basket, a pump for recirculating wash liquid from said sump into said spin basket, and a water level sensor for measuring the water level in said sump and providing an output, said method comprising: determining a size of a laundry load held in said spin basket based on analysis of changing water level in the sump.
 28. A method as claimed in claim 27 wherein said analysis relating to the rate at which free wash liquid drains from a saturated laundry load and collects in said sump and/or the volume of free wash liquid held by the saturated clothes load during recirculation.
 29. A method as claimed in either claim 27 or claim 28 wherein said analysis uses water level output from said sensor under two operating conditions: with the pump recirculating wash liquid into the spin basket, and with the pump not recirculating wash liquid into the spin basket.
 30. A method as claimed in either claim 27 or claim 28 wherein said analysis uses water level output from said sensor read on at least two occasions, at least one said occasion being after ceasing to recirculate wash liquid in the spin basket.
 31. A method as claimed in claim 30 wherein said controller is programmed to determine a size of a laundry load held in said spin basket by comparing a first water level output taken while recirculating water through said wash basket with a second water level output taken after ceasing to recirculate water through said wash basket.
 32. A method as claimed in claim 31 wherein said second water level output is taken a predetermined time after ceasing to recirculate wash liquid through said basket.
 33. A method as claimed in claim 31 wherein said second water level output is taken at a time when free liquid in the laundry load would not be expected to be completely drained to the sump for any of the normal washload sizes. 